This invention relates to temperature control systems, and in particular to thermostats having two operating control modes.
In many temperature control systems it is desirable to provide alternative modes of temperature control and means for selecting the desired control mode. Such temperature control systems are especially useful in large public buildings, such as schools, hospitals, and office buildings, in which respective rooms or distinct building areas are provided with individual thermostats. To achieve two-mode temperature control in such cases without the expense, inefficiency, and complexity of providing separate controls for each control mode, the individual thermostats are provided with means for locally accomplishing two-mode thermostatic control and with means for switching from one temperature control mode to the other in response to a signal from a central control station.
Throughout this disclosure "control mode" means a specific manner of controlling temperature. For example, in office buildings one control mode is generally provided during business hours, and another control mode is provided for nights, weekends, and holidays, periods when the building is generally not occupied. Similarly, in another application one control mode can be the heating cycle, and the second control mode can be the cooling cycle.
An efficient system for controlling temperature in two operating modes and for switching numerous thermostats located in various locations from one operating mode to the other in response to a central control signal is disclosed in the U.S. Pat. No. 3,305,172, which is incorporated herein by reference. In that system the central control station can provide pressure signals of two magnitudes. If the pressure signal of a low magnitude is transmitted from the central control source, all thermostats receiving that signal operate in the first control mode. When the low magnitude pressure signal is replaced by a high magnitude pressure signal, the thermostats receiving that signal automatically switch to the second mode of operation which is maintained until a low magnitude pressure signal is again transmitted from the central control source.
The present invention provides an improved thermostat of the type disclosed in U.S. Pat. No. 3,305,172, for use in the temperature control systems having two control modes of operation. The improved thermostat of the present invention provides solutions to problems generated by the energy conservation programs. It greatly enhances the enforceability and reduces the cost of such programs. For example, government rules and regulations set certain limits as to maximum temperatures in government offices during the winter and as to minimum temperature during the summer. These rules are subject to change in certain circumstances as during energy shortages caused by severe weather, strikes, etc. Similarly, private industry and business, in order to save costs and to promote energy conservation, set its own rules regarding thermostat settings which are also subject to change. Since in most buildings there are numerous thermostats located in different rooms, the checking of the settings of thermostats, and the adjustments of the settings to comply with current rules is a time-consuming task. Any improvement which permits a quicker determination of settings and a more effecient adjustment of the settings, is of immense value. Another reason for occasional checking and adjusting of settings of thermostats is that some individuals refuse to cooperate with, and indeed, occassionally sabotage energy saving programs by changing the settings of thermostats. Thus, there is a need for a thermostat having separate set points for both modes of operation, which can be easily and efficiently inspected and/or adjusted by authorized personnel having appropriate tools, but not by occupants of the room, or are adjustable by occupants only in one of two control modes. Especially needed are thermostats having set points adjustable within predetermined limits which cannot be easily changed or cannot be changed at all.
A problem in connection with thermostats having heating and cooling control modes is that such thermostats frequently have a single set point. In a dual duct system, when the temperature exceeds the set point temperature, a single set point thermostat would activate a cooling function; whereas, when the temperature falls below the set point temperature, the thermostat would activate a heating function. Such operation often leads to waste of energy where cooling and heating are alternatively activated as the temperature of the enclosure fluctuates around the set point and in practice it may occasionaly lead to simultaneous heating and cooling of the same room.
The present invention alleviates the problems recognized by the inventors.
Thus, one object of this invention is to provide a thermostat operating in one of two control modes selected by a pressure signal from a central source, the settings of which are visible without removal or displacement of any parts of the thermostat and easily and efficiently adjustable by authorized personnel but not the occupants of the space.
Another object of the invention is to provide a two-mode thermostat having separate, clearly visible from outside, set points for each mode of operation, which set points can be easily and efficiently adjusted by occupants without removing any parts of the thermostat but only within limits set by restricting means accessible only to authorized personnel.
A further object of the invention is to provide a two-mode thermostat having in each mode of operation a separate set point which is clearly visible without removing any parts of the thermostat and which can be adjusted without removal of any parts of the thermostat but only within predetermined limits which are factory set and cannot be altered even by maintenance personnel.
Still another object of the invention is to provide a two-mode thermostat having in each mode of operation a separate, clearly visible from outside, set point which is independently adjustable only by authorized personnel and only within a predetermined temperproof temperature range without removing any parts of the thermostat.
A still further object of the invention is to provide a thermostat having in each mode of operation a separate, clearly visible, set point which is adjustable by occupants without removing any parts of the thermostat but only within predetermined limits which are permanently set.
Other objects of the invention will become apparent to those skilled in the art upon studying this disclosure.